In recent years, especially materials for forming a color image are the main current as image recording materials. Concretely, recording materials of the inkjet mode, recording materials of the thermal transfer mode, recording materials of the electrophotographic mode, transfer type silver halide photosensitive materials, printing inks, recording pens, and others are extensively utilized. Also, color filters for recording and reproducing a color image are used in imagers such as CCD in photographing instruments and in LCD and PDP in displays.
In these color image recording materials and color filters, for the sake of reproducing or recording a full color image, dyes or pigments of three primary colors of the so-called additive color mixing method or subtractive color mixing method are used. However, it is the present state that fast pigments that have an absorption characteristic such that a preferred color reproduction region can be realized and that are durable against various conditions for use are not available yet, and hence, improvements are eagerly demanded.
The inkjet recording method becomes widespread rapidly and is further developing because the material costs are cheap, high-speed recording is possible, a noise upon recording is small, and color recording is easy.
The inkjet recording method includes the continuous mode of continuously flying droplets and the on-demand mode of flying droplets corresponding to an image information signal; and the ejection mode thereof includes a mode of ejecting droplets upon application of pressure by piezoelectric devices, a mode of ejecting droplets upon generation of bubbles in the ink by heat, a mode of using ultrasonic waves, and a mode of sucking and ejecting droplets by electrostatic force.
Also, as the inkjet recording ink, aqueous inks, oily inks, or solid (melt type) inks are employed.
Pigments that are used for such inkjet recording inks are required such that solubility or dispersibility in solvent is good; high-density recording is possible; hue is good; they are fast to light, heat or active gases in the environment (such as NOx, oxidizing gases such as ozone, and SOx); fastness to water or chemicals is excellent; fixability to image receiving materials is good so that bleeding hardly occurs; preservability as the ink is excellent; they are not toxic; purity is high; and they are cheaply available.
However, it is extremely difficult to seek pigments that meet these requirements at high levels. In particular, it is strongly desired that pigments have good cyan hue and are fast to light, humidity and heat, and especially, pigments are fast to oxidizing gases such as ozone in the environment upon printing on an image receiving material having an ink receiving layer containing porous white inorganic pigment particles. Also, it is strongly desired that the pigments have good ink storage stability as described later.
As a pigment skeleton of cyan to be used for such an inkjet recording ink, those of a phthalocyanine base, an anthraquinone base, and a triphenylmethane base are enumerated, and phthalocyanine compounds having excellent hue and light fastness are used. However, the phthalocyanine compounds do not have sufficient fastness to oxidizing gases, especially ozone and cannot be satisfied with ink stability. Accordingly, improvements are demanded.
As representative phthalocyanine pigments that are most widely reported and utilized, phthalocyanine derivatives classified into the following (1) to (6) groups are enumerated.    (1) Copper phthalocyanine based pigments [for example, Cu-Pc-(SO3Na)m: a mixture of m=1 to 4] such as Direct Blue 86 and Direct Blue 87. Incidentally, the term “Pc” as used in the foregoing formula and the present specification means a phthalocyanine skeleton.    (2) Phthalocyanine based pigments [for example, Cu-Pc-(SO3Na)m(SO2NH2)n: a mixture of (m+N)=1 to 4] such as Direct Blue 199 and those described in JP-A-62-190273, JP-A-63-28690, JP-A-63-306075, JP-A-63-306076, JP-A-2-131983, JP-A-3-122171, JP-A-3-200883, and JP-A-7-138511.    (3) Phthalocyanine based pigments [for example, Cu-Pc-(CO2H)m(CONR1R2)n: (m+n)=a number of from 0 to 4] such as those described in JP-A-63-210175, JP-A-63-37176, JP-A-63-304071, JP-A-5-171085, and WO 00/08102.    (4) Phthalocyanine based pigments [for example, Cu-Pc-(SO3H)m(SO2NR1R2)n: (m+N)=a number of from 0 to 4, and m≠0] such as those described in JP-A-59-30874, JP-A-1-126381, JP-A-1-190770, JP-A-6-16982, JP-A-7-82499, JP-A-8-34942, JP-A-8-60053, JP-A-8-113745, JP-A-8-310116, JP-A-10-140063, JP-A-10-298463, JP-A-11-29729, JP-A-11-320921, EP173476A2, EP468649A1, EP559309A2, EP596383A1, DE3411476, U.S. Pat. No. 6,086,955, WO 99/13009, and GB2341868A.    (5) Phthalocyanine based pigments [for example, Cu-Pc-(SO3H)l(SO2NH2)m(SO2NR1R2)n: (l+m+N)=a number of from 0 to 4] such as those described in JP-A-60-208365, JP-A-61-2772, JP-A-6-57653, JP-A-8-60052, JP-A-8-295819, JP-A-10-130517, JP-A-11-72614, JP-T-11-515047, JP-T-11-515048, EP196901A2, WO 95/29208, WP 98/49239, WO 98/49240, WO 99/50363, and WO 99/67334.    (6) Phthalocyanine based pigments [for example, Cu-Pc-(SO2NR1R2)n: n=a number of from 1 to 5] such as those described in JP-A-59-22967, JP-A-61-185576, JP-A-1-95093, JP-A-3-195783, EP649881A1, WO 00/08101, and WO 00/08103.
Though the phthalocyanine dyes that are generally used widely at present and described in the above cited patent documents, represented by Direct Blue 87 and Direct Blue 199, are characterized in that they are excellent in light fastness as compared with magenta dyes and yellow dyes, they are liable to generate a problem caused by their solubility. For example, poor solubility is generated at the time of manufacture to cause a manufacture trouble, and a problem caused by deposition of insoluble matters at the time of product storage or use is often generated. In particular, in the inkjet recording as described previously, poor storage stability of inks such as deposition of a dye causes problems inclusive of clogging and poor ejection of printing heads, resulting in marked degradation of a printed image.
Also, these phthalocyanine dyes likely cause color fading by oxidizing gases such as ozone, the matter of which is often taken up as an environmental problem nowadays, leading a serious problem that the printing density greatly lowers.
At present, the inkjet recording is rapidly expanding in its use field. In the future, if it is widely used more and more in general homes, SOHO, business field, etc., it should be exposed to various use conditions or use environment. As a result, there will be often generated problems such that a trouble in the ink storage stability caused by poor solubility of a cyanine dye occurs and that a printed image causes color fading upon exposure to light or active gases in the environment. Accordingly, in particular, realization of pigments and ink compositions having good hue, excellent light fastness or fastness to active gases (such as NOx, oxidizing gases such as ozone, and SOx) in the environment, and high solubility is eagerly demanded more and more.
Up to date, phthalocyanine pigments to which resistance to ozone gas is given have been disclosed in, for example, JP-A-3-103484, JP-A-4-39365, and JP-A-2000-303009. However, it is the present state that any of them cannot satisfy the hue and the fastness to light and oxidizing gases at the same time. In particular, with respect to the resistance to ozone gas, nothing has been reported as to the nature of a pigment as an index thereof. Further, EP1243626A1 and EP1243627A1 report the use of phthalocyanine based pigments. However, it is the present state that since the fastness largely depends upon the density (only high-density areas are made fast), and light is reflected in the high-density areas due to occurrence of a bronze phenomenon, not only the optical density of the recorded image lowers, but also the hue of the recorded image largely differs from the desired hue, so that the required performance cannot be achieved at the satisfactory level.
Also, in the case where an azaphthalocyanine compound described in WO 02/34844 is used as an ink (especially a cyan dye), the hue of the azaphthalocyanine compound is remarkably shifted to short wavelengths. As a result, it cannot satisfy an absorption characteristic upon which a preferred color reproduction region can be realized. Further, when the central metal of a metallic phthalocyanine compound is changed (for example, to Ni), there is an effect of improving the hue (shifting to long wavelengths) to some extent. However, an absorption characteristic upon which a preferred color reproduction region can be realized cannot be satisfied yet, and a further problem occurs with respect to the material safety due to the use of Ni.
On the other hand, as an ink of the inkjet recording mode (the ink will be sometimes referred to as “inkjet recording ink”), aqueous inks are mainly used. The aqueous inks are basically constituted of a pigment, water, and an organic solvent, and from the standpoints of odors and safety to human beings and the circumferential environment, water is the main solvent. Also, as the pigment, water-soluble dyes such as acid dyes, basic dyes, reactive dyes, and direct dyes are generally used.
Such inkjet recording inks (and dyes) are required to have various characteristics described below.    (1) Physical property values of the ink in viscosity, surface tension, specific electric conductivity, density, pH, etc. are proper.    (2) Long-term storage stability of the ink is good.    (3) Dissolution components have high dissolution stability so that clogging of nozzles does not occur.    (4) The ink is quickly dried on a material to be recorded.    (5) The recorded image is clear and good in resistance to light and resistance to water.
However, the conventional inks have not satisfied all of these characteristics yet.
In the case of usually used aqueous inks, water-soluble dyes are used. For that reason, in the case where water splashes on the recorded image, there is generated a big problem in resistance to water such that the dye elutes or the recorded image bleeds or disappears. In particular, occurrence of clogging of heads in the inkjet recording mode is problematic, and at present, various investigations on the ink storage stability as the main purpose are being made.
For example, a method in which an organic solvent or resin is added to an ink using a pigment or an oil-soluble dye as a pigment or an aqueous ink using a water-soluble dye is being investigated. However, the ink using a pigment involves problems such that it is poor in dispersion stability and inferior in storage stability and that it causes clogging of nozzles. Also, since the ink using an oil-soluble dye uses an organic solvent, it involved a problem in environmental hygiene such as odors and a problem such that bleeding of the ink is large, leading to a lowering in image quality. Also, even in the case of inks to which additives have been added, there were involved problems such that the storage stability is inferior, clogging of nozzles occurs, and the inks becomes viscous so that flying of the ink is poor.
The inks disclosed in JP-A-2000-303014 and JP-A-2000-313837 are concerned with phthalocyanine pigments having improved dispersion stability and exhibiting excellent storage stability but cannot meet the hue and the fastness to light and oxidizing gases at the same time. As a result, these inks have not yet become a product that can satisfy the requirements in the market.
Recently, JP-A-6-340835, JP-A-12-239584, and WO 00/08102 describe inks using an aqueous dispersion comprising, as a dispersoid, a polyester resin colored with a dye or a pigment. However, even by utilizing this method, the foregoing problems have not been sufficiently solved yet. On the other hand, it is described that the dye is problematic in affinity with the resin, the matter of which is directly related to a lowering in image density, a lower in resistance to water, storage stability, clogging in nozzles, etc., and control in mean particle size of the colored resin finer particles.
Also, in general, as described in WO 00/17275, WO 00/08103, WO 00/08101, WO 98/41853, and JP-A-10-36471, an unsubstituted phthalocyanine compound is sulfonated, and in the case where it is used as a water-soluble dye, the sulfonated compound is used as an alkali metal salt (such as a sodium slat) thereof as it is. In the case where the sulfonated compound is derived into an oil-soluble dye, those synthesized by subjecting the sulfonated compound to sulfonyl chlorination and then amidation can be used.
In aqueous cyan inks that have hitherto been used for inkjet printing, water-soluble dyes such as copper phthalocyanine compounds comprising a sulfonated copper phthalocyanine compound having a sulfo group or a salt of a sulfo group as a substituent are used.
In that case, not only sulfonation can occur at any position on the phthalocyanine nucleus, but also control of the number of positions to be sulfonated is difficult. Accordingly, in the case of introducing a sulfo group under such reaction conditions, the position and the number of the sulfo group introduced into the product cannot be specified so that a mixture of products that are different in the number and substitution position of a substituent from each other is always obtained.
And the resulting mixture is mingled with a component having low solubility, for example, a component in which the phthalocyanine nucleus is not sulfonated or sulfonated only at one position thereof. As a result, in the case where the product is used as a water-soluble dye, its solubility is insufficient. Thus, improvements in solubility are desired.
On the other hand, phthalocyanine compounds having an ammonium salt of sulfonic acid containing an ion pair of a sulfamoyl group and/or a sulfo group and an amine compound are known as an oil-soluble dye. Such phthalocyanine compounds are produced by chlorosulfonating a metallic phthalocyanine compound with chlorosulfonic acid and reacting the resulting chlorosulfonated compound of the phthalocyanine compound with an amine compound (see, for example, Yutaka Hosoda, Riron Seizo Senryo Kagaku (Theoretical Manufacturing Dye Chemistry), 5th Edition, published on Jul. 15, 1968, Gihodo, pp. 798–799). According to this production process, in the reaction of the chlorosulfonated compound of the phthalocyanine compound with the amine compound, not only a sulfonic acid amide group is formed, but also a part of the chlorosulfonyl group is hydrolyzed and remains as a sulfo group, or a phthalocyanine compound containing an ammonium salt of sulfonic acid in wherein a pair ion of the sulfo group and the amine compound is formed is obtained.
In the case where the thus obtained phthalocyanine compound is used as an inkjet recording pigment, there are generated problems such that an ink cannot be prepared because of low solubility of the ink in a solvent and that an ink having a necessary concentration cannot be prepared. Also, due to influences of the residual sulfo group, bleeding occurred when printed on plain paper, resistance to water of the recorded image became worse, or adverse influences in other various characteristics were caused.
In the light of the above, various characteristics of inks, especially inks to be used in the inkjet recording mode largely depend upon characteristics inherent to the pigment, and it is extremely important to select a pigment that meets the foregoing various conditions.
JP-A-2003-34758 discloses a phthalocyanine compound (mixture) containing a pyridine ring, a pyrazine ring and a benzene ring. But, a phthalocyanine compound having more improved fatness (especially, to ozone gas) in which substituents and portions having substituents are limited has been needed.